This epidemiologic study is a multi-disciplinary approach to elucidate the relationship of early childhood levels of blood pressure and anthropometric measures to the development of hypertension in childhood and early adult life. An entire school district of approximately 6,000 school age children in Muscatine, Iowa, have had their plasma lipids, blood pressure, heights, weights and triceps skinfold ticknesses measured on four occasions over a period of seven years. Thus, the entire distribution of these variables are known at each school age level and the relationship of measurements on the same individual on repeated occasions can be estimated. The study plans to examine the familial and psychological factors relating to the distribution of blood pressure, and to study cardiac output and vascular resistance not only as they exist across the distribution of blood pressure but also as they are affected by orthostatic stress and sodium intake.